A known drive mechanism for a surface propeller is one in which the motor which is inboard and the shafting to the propeller is arranged on a common carrier which is swingably fastened, if desired, through damping elements near the transom plate on the hull of the watercraft and devices are provided for varying the angle of inclination of the carrier to effect a varying of the depth of immersion of the propeller. In the case of surface propellers, the entire propeller is not immersed into the water, but projects more and more out of the water with increasing travelling speed, and at a maximum speed is approximately half way out of the water.
Such a drive mechanism through which the many disadvantages of the generally known Z-drive were to be avoided, brings about very good results in practical use, in particular in the case of racing boats. Due to the significant weight of the drive motor, however, which in most cases is a diesel motor, this drive is less suitable for leisure boats.
A drive mechanism having a surface propeller is known from U.S. Pat. No. 3,933,116 in which the motor is fixedly installed within the watercraft and the shaft which supports the propeller is connected to the motor through a universal joint. The propeller shaft is supported in an arm which is provided with a cavitation plate, which arm is swingably fastened at the rear of the watercraft both about a horizontal axis for varying the depth of immersion of the propeller and also about a vertical axis for controlling the vehicle. Thus the propeller thrust must be absorbed by the various hinge pins which is a disadvantage. A further disadvantage lies in the hydraulic devices for lifting and lowering the arm which must be relatively large because of the weight of the arm.
The foregoing disadvantages are avoided when the arm is secured rigidly with the propeller to the watercraft and the depth of immersion of the propeller is controlled by a trim rudder which is pivotal about a horizontal axis and which is connected to the cavitation plate. Such a device is known from U.S. Pat. No. 4,031,846. Due to the fact that the propeller thrust bearing is arranged within the watercraft in that device, the propeller shafts thus are supported partly in the vehicle and partly in the arm, as a result of which installation and removal of the arm are made more difficult. In addition, the devices which are needed for the operation of the rudder for controlling the vehicle are externally exposed on the arm, where they can be easily damaged and are not appealing in appearance, and appearance is desirable today, particularly in the case of leisure boats.
Starting out from this observation, the basic purpose of the invention is to provide a drive mechanism for a watercraft having a surface propeller in which the arm which supports the propeller shaft and the propeller is one complete structural unit, which unit is easily and efficiently mountable as a whole on the watercraft and which transmits the propeller thrust directly onto the vehicle rather than through other aggregate components. Aside from this, it is a purpose of this invention to provide a drive mechanism, as aforesaid, which has a closed appearance and is simple and inexpensive to manufacture.
These purpose are attained by a drive mechanism of the above-mentioned type in which the part of the shafting which supports the propeller is supported outside of the watercraft in a support arm secured rigidly to the vehicle by a flange plate, and a thrust bearing is housed within the support arm for transmitting the propeller thrust only through rigid parts and a large surface onto the watercraft. This drive mechanism is easily and efficiently manufactured and safe to operate, particularly when the support arm is of unitary construction, as this assures a high degree of rigidity and offers furthermore a stylistic design for the aggregate.
The thrust bearing keeps the propeller thrust away from the motor and instead is directs it on the shortest path to the hull of the watercraft. By arranging the propeller shaft thrust bearing in a bearing sleeve, the life expectancy of the bearings is increased by the use of low friction bearings which run in an oil bath provided in the bearing sleeve. A flange connection between the propeller shaft and the part of the shafting which is provided within the watercraft permits, simple installation and removal and allows use of an elastic coupling to compensate for angular deflections and alignment errors.
It is possible to arrange behind the propeller a blade of a steering rudder which is supported swingably on the support arm, with which blade the watercraft is controlled. Control pipelines and linkages for the rudder can be placed within the support arm so that they do not interfere with the flow of water and are protected from damage.